CN113019137B - Preparation and application of MXene @ COF composite film - Google Patents

Abstract

The invention provides a preparation method and application of an MXene @ COF composite film, which are used for separation of dyes. The MXene @ COF composite film is obtained by electrostatic self-assembly of MXene and COF with different mass ratios in an aqueous solution and finally suction filtration. The composite membrane prepared by the method is simple in preparation process, solves the problem of low filtration speed of the Mxene membrane, and has important application value in the field of dye separation.

Description

Preparation and Application of MXene@COF Composite Membrane

technical field

The invention belongs to the field of separation, and in particular relates to the preparation of MXene@COF composite membranes.

Background technique

With the rapid development of the industry, the demand for organic dyes is also increasing. According to reports, the global dye production has exceeded 7 × 105 tons. Organic dyes in sewage are difficult to degrade and cause great harm to the environment and human health. Therefore, it is of great significance to develop a green, non-toxic and high-adsorption adsorbent. Chemical precipitation, ion exchange, electrochemistry, membrane filtration and adsorption are currently recognized as the main methods for removing dyes from aqueous solutions. The chemical precipitation in it will produce a lot of scum, which will be treated badly. Ion exchange resins are expensive and cannot be used on a large scale. Electrochemical methods are expensive and inefficient. Membrane filtration has high efficiency and low energy consumption. The adsorption method is a promising adsorption technology due to its simple design, flexible application and high selectivity.

COFs are a new class of crystalline porous materials composed of covalently linked organic units. Due to their unique properties, such as intrinsic porosity, well-defined pore size, ordered channel structure, large surface area, excellent thermochemical stability, and multiple functions, COFs have attracted tremendous attention in many fields in recent years. concerns, including gas storage, molecular separation, catalysis, and energy storage. In particular, the unique pore structure of COFs provides high-flux properties in filtration membranes, making them an excellent candidate for building molecular sieve membranes with excellent performance.

MXenes are a family of new 2D materials based on transition metal carbides and/or nitrides, which are widely used in the fields of energy storage, smart materials, and selective ion sieves due to their complex, diverse structural, mechanical, physical, and chemical properties. The layered structure and hydrophilicity of MXene membranes can realize the separation of water molecules and dyes, but their filtration efficiency is limited due to the small interlayer spacing and small water flux of MXene membranes. If COF and Mxene can still be combined, the water flux of the composite membrane can be improved, and the filtration effect of dyes can be maintained, which will greatly improve the filtration performance.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a preparation method of Mxene/COF composite membrane in view of the problem of small water flux of MXene membrane. The invention utilizes the principle of electrostatic self-assembly of positively charged COF-LZU1 and negatively charged Mxene to prepare the Mxene/COF composite film.

The technical scheme adopted in the present invention is as follows:

(1) Preparation of Ti ₃ C ₂ T _X : Ti ₃ C ₂ T _X was prepared by selectively etching 2 g of Ti ₃ AlC ₂ precursor powder using an etchant containing 2.0 g of LiF and 40 mL of aqueous HCl (9M). The etching process was stirred at 35° C. for 24 hours, then the resulting solution was washed with deionized water and centrifuged at 3500 rpm until the pH reached ~5 to obtain a stripped Ti ₃ C ₂ T _X sheet solution. _{The Ti3C2TX concentration} was calculated from the weight of the _{dried Ti3C2TX thin} film.

(2) Preparation of COF-LZU1: Take 100 mg of trimesicaldehyde and 100 mg of p-phenylenediamine, dissolve in 20 ml of dioxane, then slowly add 0.4 ml of 3mol/L acetic acid solution, seal and let stand for three days. After the reaction was completed, the precipitate was washed three times with methanol, and then vacuum-dried to obtain COF-LZU1 powder.

(3) Preparation of Mxene/COF composite membrane: The total mass of Mxene and COF was fixed at 3 mg. Different proportions of MXene and COF-LZU1 were blended in 20 mL of deionized water, and then ultrasonically vibrated for 10 min to disperse the mixture. After fully stirring the MXene and COF solution (suspension) for 12 h, it was sonicated for another 10 min to ensure homogeneity. The mass ratios of the Mxene/COF composite membranes were 1:0, 8:1, 4:1, 2:1, 1:1, and 1:2, respectively.

Preferably, the mass ratio of MXene to COF is 1:0, 8:1, 4:1, 2:1, 1:1, 1:2, and the MXene@COF composite membrane prepared within this ratio range can filter dyes The effect is better.

The application of MXene@COF composite membrane, as a separation material, in dye separation was tested by a mixed dye solution selective separation experiment. That is, the dye is passed through the composite membrane, and the composition of the solution before and after passing through is analyzed.

Compared with the previous related literature reports, the application of the MXene@COF composite membrane of the present invention in dye separation has the following advantages:

(1) In view of the relatively slow filtration speed of MXene membrane, and the nano-scale porous structure of COF has advantages in terms of filtration speed, by combining Mxene and COF to prepare MXene@COF composite membrane, Mxene membrane can overcome Mxene The problem of relatively slow membrane filtration speed;

(2) Mxene is negatively charged in the aqueous solution of Ph=7, while COF is positively charged. The combination of Mxene and COF can be realized by electrostatic self-assembly, and the experimental process is simple.

Description of drawings

Figure 1 shows the infrared spectrum of the MXene@COF composite film;

Figure 2 is a scanning electron microscope image of the MXene@COF composite film;

Detailed ways

Example 1

Preparation _{of Ti3C2TX} : _Ti3C2TX was prepared by selectively etching _{2 g} of _Ti3AlC2 precursor powder using an etchant containing _2.0 g of LiF and 40 mL of aqueous HCl ( _9M ). The etching process was stirred at 35°C for 24 hours, then the resulting solution was washed with deionized water and centrifuged at 3500 rpm until the pH reached ~5, to obtain a stripped Ti ₃ C ₂ T _X sheet solution. _{The Ti3C2TX concentration} was calculated from the weight of the _{dried Ti3C2TX thin} film.

Preparation of COF-LZU1: Take 100 mg of trimesicaldehyde and 100 mg of p-phenylenediamine, dissolve in 20 ml of dioxane, then slowly add 0.4 ml of 3mol/L acetic acid solution, seal and let stand for three days. After the reaction was completed, the precipitate was washed three times with methanol, and then vacuum-dried to obtain COF-LZU1 powder.

Preparation of Mxene/COF composite membrane: The total mass of Mxene and COF was fixed at 3 mg. Different proportions of MXene and COF-LZU1 were blended in 20 mL of deionized water, and then ultrasonically vibrated for 10 min to disperse the mixture. After fully stirring the MXene and COF solution (suspension) for 12 h, it was sonicated for another 10 min to ensure homogeneity. The mass ratios of Mxene/COF composite membranes were 1:0, respectively.

Example 2

Preparation _{of Ti3C2TX} : _Ti3C2TX was prepared by selectively etching _{2 g} of _Ti3AlC2 precursor powder using an etchant containing _2.0 g of LiF and 40 mL of aqueous HCl ( _9M ). The etching process was stirred at 35° C. for 24 hours, then the resulting solution was washed with deionized water and centrifuged at 3500 rpm until the pH reached ~5 to obtain a stripped Ti ₃ C ₂ T _X sheet solution. _{The Ti3C2TX concentration} was calculated from the weight of the _{dried Ti3C2TX thin} film.

Preparation of COF-LZU1: Take 100 mg of trimesicaldehyde and 100 mg of p-phenylenediamine, dissolve in 20 ml of dioxane, then slowly add 0.4 ml of 3mol/L acetic acid solution, seal and let stand for three days. After the reaction was completed, the precipitate was washed three times with methanol, and then vacuum-dried to obtain COF-LZU1 powder.

Preparation of Mxene/COF composite membrane: The total mass of Mxene and COF was fixed at 3 mg. Different proportions of MXene and COF-LZU1 were blended in 20 mL of deionized water, and then ultrasonically vibrated for 10 min to disperse the mixture. After fully stirring the MXene and COF solution (suspension) for 12 h, it was sonicated for another 10 min to ensure homogeneity. The mass ratio of the prepared Mxene/COF composite films was 8:1, respectively.

Example 3

Preparation _{of Ti3C2TX} : _Ti3C2TX was prepared by selectively etching _{2 g} of _Ti3AlC2 precursor powder using an etchant containing _2.0 g of LiF and 40 mL of aqueous HCl ( _9M ). The etching process was stirred at 35° C. for 24 hours, then the resulting solution was washed with deionized water and centrifuged at 3500 rpm until the pH reached ~5 to obtain a stripped Ti ₃ C ₂ T _X sheet solution. _{The Ti3C2TX concentration} was calculated from the weight of the _{dried Ti3C2TX thin} film.

Preparation of COF-LZU1: Take 100 mg of trimesicaldehyde and 100 mg of p-phenylenediamine, dissolve in 20 ml of dioxane, then slowly add 0.4 ml of 3mol/L acetic acid solution, seal and let stand for three days. After the reaction was completed, the precipitate was washed three times with methanol, and then vacuum-dried to obtain COF-LZU1 powder.

Preparation of Mxene/COF composite membrane: The total mass of Mxene and COF was fixed at 3 mg. Different proportions of MXene and COF-LZU1 were blended in 20 mL of deionized water, and then ultrasonically vibrated for 10 min to disperse the mixture. After fully stirring the MXene and COF solution (suspension) for 12 h, it was sonicated for another 10 min to ensure homogeneity. The mass ratio of the prepared Mxene/COF composite films was 4:1, respectively.

Example 4

Preparation _{of Ti3C2TX} : _Ti3C2TX was prepared by selectively etching _{2 g} of _Ti3AlC2 precursor powder using an etchant containing _2.0 g of LiF and 40 mL of aqueous HCl ( _9M ). The etching process was stirred at 35° C. for 24 hours, then the resulting solution was washed with deionized water and centrifuged at 3500 rpm until the pH reached ~5 to obtain a stripped Ti ₃ C ₂ T _X sheet solution. _{The Ti3C2TX concentration} was calculated from the weight of the _{dried Ti3C2TX thin} film.

Preparation of COF-LZU1: Take 100 mg of trimesicaldehyde and 100 mg of p-phenylenediamine, dissolve in 20 ml of dioxane, then slowly add 0.4 ml of 3mol/L acetic acid solution, seal and let stand for three days. After the reaction was completed, the precipitate was washed three times with methanol, and then vacuum-dried to obtain COF-LZU1 powder.

Preparation of Mxene/COF composite membrane: The total mass of Mxene and COF was fixed at 3 mg. Different proportions of MXene and COF-LZU1 were blended in 20 mL of deionized water, and then ultrasonically vibrated for 10 min to disperse the mixture. After fully stirring the MXene and COF solution (suspension) for 12 h, it was sonicated for another 10 min to ensure homogeneity. The mass ratios of the Mxene/COF composite membranes were 2:1, respectively.

Example 5

Preparation _{of Ti3C2TX} : _Ti3C2TX was prepared by selectively etching _{2 g} of _Ti3AlC2 precursor powder using an etchant containing _2.0 g of LiF and 40 mL of aqueous HCl ( _9M ). The etching process was stirred at 35° C. for 24 hours, then the resulting solution was washed with deionized water and centrifuged at 3500 rpm until the pH reached ~5 to obtain a stripped Ti ₃ C ₂ T _X sheet solution. _{The Ti3C2TX concentration} was calculated from the weight of the _{dried Ti3C2TX thin} film.

Preparation of COF-LZU1: Take 100 mg of trimesicaldehyde and 100 mg of p-phenylenediamine, dissolve in 20 ml of dioxane, then slowly add 0.4 ml of 3mol/L acetic acid solution, seal and let stand for three days. After the reaction was completed, the precipitate was washed three times with methanol, and then vacuum-dried to obtain COF-LZU1 powder.

Preparation of Mxene/COF composite membrane: The total mass of Mxene and COF was fixed at 3 mg. Different proportions of MXene and COF-LZU1 were blended in 20 mL of deionized water, and then ultrasonically vibrated for 10 min to disperse the mixture. After fully stirring the MXene and COF solution (suspension) for 12 h, it was sonicated for another 10 min to ensure homogeneity. The mass ratios of the Mxene/COF composite membranes were 1:1, respectively.

Example 6

Preparation _{of Ti3C2TX} : _Ti3C2TX was prepared by selectively etching _{2 g} of _Ti3AlC2 precursor powder using an etchant containing _2.0 g of LiF and 40 mL of aqueous HCl ( _9M ). The etching process was stirred at 35° C. for 24 hours, then the resulting solution was washed with deionized water and centrifuged at 3500 rpm until the pH reached ~5 to obtain a stripped Ti ₃ C ₂ T _X sheet solution. _{The Ti3C2TX concentration} was calculated from the weight of the _{dried Ti3C2TX thin} film.

Preparation of COF-LZU1: Take 100 mg of trimesicaldehyde and 100 mg of p-phenylenediamine, dissolve in 20 ml of dioxane, then slowly add 0.4 ml of 3mol/L acetic acid solution, seal and let stand for three days. After the reaction was completed, the precipitate was washed three times with methanol, and then vacuum-dried to obtain COF-LZU1 powder.

Preparation of Mxene/COF composite membrane: The total mass of Mxene and COF was fixed at 3 mg. Different proportions of MXene and COF-LZU1 were blended in 20 mL of deionized water, and then ultrasonically vibrated for 10 min to disperse the mixture. After fully stirring the MXene and COF solution (suspension) for 12 h, it was sonicated for another 10 min to ensure homogeneity. The mass ratios of the Mxene/COF composite membranes were 1:2, respectively.

Dye separation (physical separation) experiment: prepare 50mg/L methyl green, ethyl violet, methyl violet, basic fuchsine, methylene blue solutions, respectively, take the same volume of the above dye solutions and mix together a total of 1000mL, pass through The filtration performance of the ^Mxene /COF composite membrane was measured by nanofiltration using a filtration device with an effective membrane area of 13.85 cm. The working pressure is controlled at 0.1MPa. The filter system was filtered for a period of time until a steady state was reached before measurement. The absorbance was measured with a UV spectrophotometer, and the concentration of the remaining dye was calculated from the absorbance. Different experiments were performed three times for each group, and the average of the three results was taken.

There will be a corresponding equation for absorbance and dye concentration. Substitute the obtained absorbance to obtain the corresponding remaining dye concentration, dye separation rate or adsorption rate (%) = (initial dye concentration - remaining dye concentration) / initial dye concentration .

The results are shown in Table 1:

Table 1

Claims (2)

1. The preparation method of MXene@COF composite membrane, it is characterized in that described method comprises the following steps: (1) Preparation of Ti ₃ C ₂ T _X : Ti ₃ C ₂ T _X was prepared by selectively etching 2 g of Ti ₃ AlC ₂ precursor powder using an etchant containing 2.0 g LiF and 40 ml of 9 mol/L HCl aqueous solution, etching The process was stirred at 35 °C for 24 hours, then the resulting solution was washed with deionized water and centrifuged at 3500 rpm until the pH reached 5, that is, the exfoliated Ti ₃ C ₂ T _X flake solution was obtained. Ti ₃ C ₂ T _X concentration calculated by weight of Ti ₃ C ₂ T _X thin film; (2) Preparation of COF-LZU1: take 100mg trimesicaldehyde and 100mg p-phenylenediamine, dissolve in 20ml dioxane, slowly add 0.4ml 3mol/L acetic acid solution, seal and let stand for three days, after the reaction is completed , washed the precipitate three times with methanol, and then vacuum-dried to obtain COF-LZU1 powder; (3) Preparation of Mxene/COF composite membrane: the total mass of Mxene and COF was fixed at 3 mg, different proportions of MXene and COF-LZU1 were blended in 20 ml of deionized water, then ultrasonically vibrated for 10 min to disperse the mixture, and the MXene was fully stirred After 12h with COF suspension solution, ultrasonic for 10min to ensure homogeneity, the mass ratio of Mxene/COF composite membrane was 8:1, 4:1, 2:1, 1:1, 1:2, respectively. 2. the application of the prepared Mxene/COF composite membrane of claim 1, is characterized in that the prepared Mxene/COF composite membrane is used as separation material, in dye separation, is tested by mixed dye selective separation, adsorption experiment: about concentration Methyl green, methylene blue, basic fuchsin, ethyl violet, methyl violet and other mixed dyes of 50 mg/L were passed through the composite membrane. When the Mxene/COF mass ratio of the composite membrane was 8:1, the Mxene/COF composite The membrane separation rate is 99.7%; when the Mxene/COF mass ratio of the composite membrane is 4:1, the Mxene/COF composite membrane separation rate is 98.8%; when the Mxene/COF mass ratio of the composite membrane is 2:1, the Mxene/COF composite membrane The membrane separation rate is 59.8%; when the Mxene/COF mass ratio of the composite membrane is 1:1, the Mxene/COF composite membrane separation rate is 37.7%; when the Mxene/COF mass ratio of the composite membrane is 1:2, the Mxene/COF composite membrane The membrane separation rate was 27.9%.

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